The present invention relates, in general, to the field of devices for leak testing the chamber.
Leak tests are generally carried out using leak detectors operating either by direct pumping or by sniffing.
The test is easy to carry out when the issue is one of checking the tightness of a closed chamber or when it relates to small-sized parts.
However, problems arise when the tightness of a component with a circular weld performed on a very long tube has to be tested and when, in addition, the environment is configured in such a way as to limit accessibility. Access to the interior of the tube is then impossible to have, and it is necessary to envision a test by sniffing from the outside, but the limit on sensitivity of this technique is of the order of 10xe2x88x927 [mbar.l.sxe2x88x921] and entails taking extreme precautions in carrying it out.
Document U.S. Pat. No. 2,766,614 discloses a device for leak testing a chamber, configured as an openable clamp capable, in the functional position, of sealingly enclosing all or part of the chamber so as to define, around the latter, a sniffing enclosure.
However, although in its functional principle, such a device is able to give satisfaction, its embodiment, as proposed in that document, is in the form of a flexible strip that can be wound into a clamp with its ends being sealingly locked around the chamber using straps: such an embodiment does not give rise to conditions suitable for obtaining sensitivity greater than those known hitherto through other means, and its practical embodiment is delicate and does not seem able to allow intensive use under industrial conditions.
The object of the invention is to propose a leak test device which, adopting the same basic design, is far more robust from the mechanical point of view, yields tightness conditions of greater quality and leads to appreciably improved sensitivity, while at the same time being able to meet the requirements of intensive industrial use.
To these ends, the invention proposes a device for leak testing a chamber, which device is shaped as an openable clamp capable, in the functional position, of sealingly enclosing all or part of the chamber so as to define, around the latter, a sniffing enclosure, which device, being arranged according to the invention, is characterized in that it comprises
a rigid bearing framework made up of several sections articulated together to allow the clamp to be opened up while it is being placed on the chamber or removed therefrom, said framework being shaped in the form of a trough with, in cross section, the overall shape of a U open radially toward the inside,
and
a jacket made of relatively flexible material, supported by said framework and shaped, at the edges of the trough formed by the framework, into deformable sealing lips able to press sealingly against the surface of the chamber.
Advantageously, the rigid bearing framework is made of metal, particularly of aluminum alloy.
In one practical exemplary embodiment, the rigid bearing framework consists of four sections connected one after the other by three articulations which are offset by about 90xc2x0 from each other.
In the course of testing, the pumping within the chamber plays a part in pressing the framework around the chamber and therefore in holding the device in a functional position around the chamber; however, it is preferable to provide locking means for holding the clamp in the sealed closed position around the chamber that is to be tested, even if only to hold the device in place before the pumping means are started up.
In order for the sealing lips to have the relative flexibility they need to press sealingly against the chamber while at the same time maintaining the necessary relative hardness to prevent excess fatigue and prevent ultimate rupture of these lips if a very strong vacuum is pulled, the relatively flexible material of which the jacket is made needs to have a shore hardness of about 40.
In one practical exemplary embodiment which is advantageous on account of its simplicity of production and the ease with which it affords sealing in spite of the presence of the articulation, the jacket consists of a plastic material which externally overmolds the rigid framework.
Likewise, in order to be sure of obtaining a sufficiently good seal even in the presence of a very strong vacuum, provision is made for the sealing lips to project beyond the respective edges of the rigid trough and to be widened so as to define a relatively broad face for bearing on the surface of the chamber.
The device according to the invention as has just been described makes it possible to detect leaks at the limit of sensitivity of the detector (of the order of 10xe2x88x929 or 10xe2x88x9210 [mbar.l.sxe2x88x921]). This remarkable performance is due in particular to the self-sealing property afforded by adhesion of the flexible lips of the sealing jacket to the chamber (for example to the periphery of the tube) in proportion to the strength of the vacuum created by pumping, this being true regardless of the surface faults of the chamber.
Because of its one-piece and rigid structure, this device is the only part that has to be handled and, furthermore, it can be handled by just one operator; it can be fitted quickly because of its ease of opening and because it can be opened far wider than the size of the chamber, particularly in the diameter of a tube, and this ease of opening allied with its compactness makes it easy to install in areas which are difficult to access (jumble of tubes, installations frequently modified, etc.).
No seal is attached: there is therefore no risk of trapping a seal which, here again, simplifies the conditions of fitting and functionally operating the device.
The small volume of the chamber means that it can be evacuated quickly and the leakage rate can be measured almost immediately.
In addition, the very architecture of the device allows it to be mounted on chambers of highly diverse shape, and in particular, on tubes regardless of their length and regardless of their diameter, including in the case where the device is mounted straddling a connection between tubes of different diameters.
Ultimately, the intervention time for performing the leak test is appreciably reduced and the results obtained are more reliable than in a conventional sniffing method.